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Otto and Diesel Cycle01:27

Otto and Diesel Cycle

An Otto engine is a four-stroke engine that uses a mixture of gasoline and air as the working fuel. The fuel is injected into the cylinder, and the piston is moved completely down so that the cylinder is at maximum volume. By moving the piston up, adiabatic compression takes place. The spark plug ignites the gasoline-air mixture, and the burning fuel adds heat to the system at a constant volume. The heated mixture expands adiabatically and gets further cooled by exhausting heat, and this cyclic...
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Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators
09:23

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Published on: May 30, 2014

Coupled quantum Otto cycle.

George Thomas1, Ramandeep S Johal

  • 1Indian Institute of Science Education and Research Mohali Transit Campus: MGSIPAP Complex, Sector 26, Chandigarh 160019, India. george@iisermohali.ac.in

Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|April 27, 2011
PubMed
Summary
This summary is machine-generated.

This study explores a quantum heat engine using two spin-1/2 systems. The coupled model shows efficiency exceeding the uncoupled version, with a tighter bound than Carnot efficiency.

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Area of Science:

  • Quantum thermodynamics
  • Condensed matter physics
  • Statistical mechanics

Background:

  • Quantum heat engines offer potential for high efficiency.
  • The Heisenberg model is a fundamental system for studying quantum interactions.

Purpose of the Study:

  • Investigate the performance of a quantum heat engine based on the Heisenberg model.
  • Analyze the efficiency and thermodynamic properties of a two-spin system.

Main Methods:

  • Utilized a four-step Otto cycle for the quantum heat engine.
  • Varied external magnetic fields while keeping coupling constant fixed during adiabatic steps.
  • Analyzed local effective temperatures of individual spins.

Main Results:

  • Achieved engine efficiency surpassing the uncoupled model.
  • Identified conditions for enhanced efficiency, including an upper bound tighter than the Carnot limit.
  • Discovered a feasible parameter domain not present in interaction-free models.
  • Observed local heat flow opposing the global temperature gradient.

Conclusions:

  • Coupling in the Heisenberg model can enhance quantum heat engine efficiency.
  • Local spin temperatures reveal complex thermodynamic behavior.
  • The model provides insights into quantum thermodynamics beyond classical limits.